1. Field of the Invention
The present invention relates to an unwrapping apparatus for unwrapping a stretch-wrapped load comprised of a pallet, a plurality of articles palletized on the pallet and a stretchable film wrapping the articles and the pallet together, and in particular, the present invention relates to an improved unwrapping apparatus for unwrapping a stretch-wrapped load by cutting a stretchable film of the stretch-wrapped load and removing it without shrinkage of the stretchable film until the film is completely separated from the palletized articles.
2. Description of the Related Art
Conventionally, a variety of empty containers, such as glass bottles, PET bottles (polyethylene terephthalate bottles), or metallic cans are delivered to a bottling plant in the form of a load in which containers are placed on a pallet in bulk and layered via separate sheets between the layers, and the load is shrink wrapped or stretch wrapped using a stretchable film. Shrink wrapping apparatuses and stretch wrapping apparatuses that can automatically shrink wrap or stretch wrap empty containers are known.
The shrink wrapped or stretch-wrapped load must be unwrapped upon reaching a user. There are known unwrapping apparatuses for automatically unwrapping a shrink wrapped or stretch-wrapped palletized load and disclosed in, for example, the Japanese Unexamined Patent (Kokai) No. 48-58995, No. 49-95788, No. 1-111642, and No. 2-166033.
However, when a shrink wrapped or stretch-wrapped palletized load is unwrapped, which includes light and empty containers placed on a pallet in bulk and layered via separate sheets, containers i.e., the wrapped articles sometimes fall off the separate sheets, because in stretch wrapping, the elastic stretchable film is generally horizontally wound around the articles under tension and enter any gaps between the vertically adjacent separate sheets so as to be in contact with the articles, and when the stretchable film is cut in this condition, the stretchable film suddenly shrinks owing to an immediate tension release of the stretchable film maintained in contact with the surfaces of the articles, resulting in the articles comprising light and empty containers stacked in bulk via separate sheets being pulled and moved by the stretchable film and possibly falling from the separate sheets In addition, when the cut stretchable film is removed from the load, sudden shrinkage of the stretchable film may occur owing to an immediate tension release at a location where the stretchable film contacts the articles, resulting in a similar situation. It is known from experience that the above described phenomenon occurs most frequently at the uppermost four corners of the stretch-wrapped load.
The unwrapping apparatuses described in the above Patent Publications do not have an appropriate means to solve this problem and are not adapted for unwrapping the stretch-wrapped load in which light and empty containers are placed in bulk on a pallet and layered via separate sheets.
Further, these unwrapping apparatuses do not have means to compress and compact the stretchable film that is cut and removed from the unwrapping apparatus so as to facilitate step thereby disposing of the stretchable film, and additional manpower is necessary to dispose of the bulky stretchable film.
To solve the above described problems, Japanese Patent Application No. 3-27726 (and the corresponding U.S. patent application Ser. No. 771,629, now U.S. Pat. No. 5,148,651) assigned to the same assignee as the present case discloses an unwrapping apparatus that prevents shrinkage of the stretchable film contacting the wrapped articles, whereby, when the load is unwrapped, the wrapped articles, such as empty containers contacting the stretchable film, are prevented from being pulled and moved by the stretchable film and thus falling down from the separate sheets (in particular, the uppermost four corners of the load), and the stretchable film is compressed and compacted after removing said film from the load.
However, even in the unwrapping apparatus disclosed in the above described Japanese Patent Application No. 3-27726, if very light empty containers such as PET bottles are wrapped by a relatively highly tacky stretchable film, the wrapped empty containers at the uppermost rear corners (viewed in the unwrapping apparatus) of the stretch-wrapped load rarely fall down when the load is unwrapped.